weird lump above lump area

HELP.... I hate to ask..
Our Black cochin hen seems to have a problem...
She is eating and walking all over BUT as everyone
got cooled off by the frozen bottles and misters in the
yard she was still panting... Then I thought I saw her
but. Now you all know they have huge fluffy butts so
I thought that was wrong. YES it was wrong. She has
some type of swollen round lump kind of high above her
vent. I soaked her in some cool water and she seemed
stop pantting but went right back to it as soon as we put
her in a kennel. Is this maybe just the heat or should I
worry?